Hardened metallic structure



Patented Feb; 13, 1951 UNITED STATES PATENT OFFICE HARDENED METALLIC STRUCTURE Howard E. Somes, Detroit, Mich, assignor, by

mesne assignments, to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio 2 Claims.

This invention relates to hardened metallic structures and particularly to tubular structures adapted to withstand sudden loads and high pressures.

An object of this invention is to provide a metallic structure, which is particularly adapted for use in tubing form, of such structural characteristics as provide an article of great resistance to suddenly applied loads and bursting pressures, in which trapped stresses are largely avoided, and which has great resistance to the starting of surface cracks under repeatedly applied loads.

The above and other objects which will be apparent are accomplished by the invention hereinafter described and illustrated in the accompanying drawing which is a sectional view through a tubular metallic structure illustrative of one embodiment of thisinvention.

As illustrated, the present invention is shown in the form of a tubular structure 5 of hardenable metal having a wall 6, the material of which is first heated, for example by electromagnetic induction heating, 'and quenched to produce a hardened martensitic structure having a predetermined hardness of, for example, approximately 60 to 62 Rockwell C.

The structure is then strengthened by tempering the martensite to a hardness givin the required physical properties in that part to be subjected to the highest stress. For this purpose, the martensite may be drawn back, for example, to a hardness range of approximately 50 to 55 Rockwell C. In order to permit machining of the surface of the bore, an inner zone 8 is then drawn to a degree of hardness capable of being machined, for example, a hardness of approximately 28 to 32 Rockwell C.

After drawing, the surface of the bore, formed by the inner layer 8, is machined to produce a finished surface having the desired configuration. If. for example, the structure is to form a gun tube, riflin grooves 9 are machined in the surface. Thereafter the finished surface of the tube is hardened by heating and quenching, preferably by electro-magnetic induction heating and quenching, to form a thin, hardened surface lfl which is then drawn back to the optimum hardness required for the particular use to which the structure is to be put.

The outer face ll of the tempered martensite I can be cold worked, for example by shot blasting, to place the material of the outer surface in a state of compression.

It will be apparent that the invention can be variously modified and adapted within the scope of the appended claims.

What is claimed is:

1. A one-piece integral tubular metallic struc ture of a heat-and-quench hardenable metal which where hardened is made hard by heating and quenching, said structure including an annular wall having a relatively very thin annular-inner surface zone having a high degree of hardness, an annular relatively thin zone surrounding said inner surface zone and having a relatively low degree of hardness, and an outer zone of relatively very much greater depth than and surrounding said zone of low hardness, said outer zone comprising an overwhelmingly preponderant portion of the total wall thickness and having a relatively high degree of hardness, the hardness of said outer zone being substantially uniform throughout its radial thickness said tubular structure having on its interior rifled grooves along its length and raised portions between the rifled grooves, the very thin hard layer covering the inner surfaces of the rifled grooves and raised portions therebetween and the thin soft layer being disposed immediately beneath the very thin hard layer and beneath the grooves and the raised portions therebetween. i

2. A one-piece integral tubular metallic structure of a heat-and-quench hardenable metal which where hardened is made hard by heating and quenching, said structure including an annular wall having a. relatively very thin annular inner surface zone having a high degree of hardness, an annular relatively thin zone surrounding said inner surface zone and having a relatively low degree of hardness, and an outer zone of relatively very much greater depth than and surrounding said zone of low hardness, said outer zone comprising an overwhelmingly preponderant portion of the total wall thickness and having a relatively high degree of hardness, the hardness of said outer zone being substantially uniform throughout its radial thickness, said tubular structure having grooves and raised portions between the grooves on the interior, the very thin hard layer covering the inner surfaces of the grooves and raised portions therebetween and the thin soft layer being disposed immediately beneath the very thin hard layer and beneath the grooves and the raised portions therebetween.

HOWARD E. SOMES.-

(References on following page) REFERENCES crmn Number Name am" I The following references are of record in the 2,281,334 sme5 P 1943 m of this t Dunn 8t 81. Aug. 25, 1942 $011188 Sept. 8, 1942 UNITED STATES PATENTS Y 5 2,316,110 Somes Apr, 6, 1943 Number Name Date FOREIGN. PATENTS Re. 14.820 Sallows Mar. 16, 1920 449,998 Brustlein Apr. '1, 1891 Number Country Date 460,261 Harvey Sept, 29, 91 19.167 Great Britain 8. 1903 930 927 gel-kstresser 0 190 10 363,323 Great Britain June 10, 1930 5 4, 29 Clark 4, 924 472,198 Gr at Britain Sept. 20, 1937 

